1. Field of the Invention
The present invention relates to a drug-impregnated ceramic to be embedded in an affected region of a living body in order to treat myelitis, a malignant tumor, and the like.
2. Description of the Related Art
According to a conventional method of treating myelitis, an antibiotic is administered through a vinyl tube inserted into an affected region. Using this method, however, makes it difficult to administer the antibiotic throughout all of the affected region over an extended time period, and patient is obliged to suffer from large stress or invasion.
With the aim of solving this problem, Japanese Patent Disclosure (Kokai) No. 59-101145 discloses a drug-impregnated porous ceramic having in its surface layer 10- to 500-.mu.m diameter pores the ceramic itself being composed of one or more members selected from a group consisting of calcium phosphate, alumina, zirconia and silicon nitride.
When such a drug-impregnated porous substance is embedded in an affected region, the drug exudes into the region over an extended time period, resulting in the drug being continuously administered to achieve the desired treatment. In addition, since the above ceramic is not harmful to a living body, no serious adverse effects will occur even is the ceramic remains within the body.
Nevertheless, the above conventional drug-impregnated ceramic does have the following drawbacks.
The release period and concentration of a drug impregnated in the porous ceramic into a living body are controlled by adjusting a pore size. Since the pores communicate with the outer surface of the ceramic, however, the release concentration of the drug is inevitably high immediately after the ceramic is embedded in an affected part. For this reason, since a large amount of the drug is released immediately after the ceramic is embedded, it is difficult to maintain a constant release concentration throughout an release period from immediately after the ceramic is embedded. Also, the drug release period itself is shortened.
In addition, since the above porous ceramic is not decomposed in a living body, drug components impregnated deep in the pores often remains therein unreleased. The unreleased drug is not available for treatment.
Furthermore, although the porous ceramic is harmless to a living body, it is not decomposed in a living body but remains therein as an alien substance, thereby producing a lump in an affected part. Therefore, in the case that bone formation need not be performed in the affected part, the part must be cut open to remove the ceramic after a drug is released. As a result, the patient may suffer physically, mentally, and even economically.